Ordinarily I wouldn’t get up early on a Saturday and rush to a symposium about climate change. Like a lot of people, I often feel like I’ve heard more than enough about this problem—how huge it is, how bad things are going to get in the future, and how the world’s governments can’t ever agree to cut carbon dioxide emissions (as we know we should).

But last Saturday at the AAAS meeting in San Jose, I was drawn to a session called “Going Negative: Removing Carbon Dioxide from the Atmosphere.”

Instead of gloom and doom or finger-wagging sermons to cut emissions (or else!), maybe I’d hear some new ideas and solutions. Maybe someone’s developed a technological poisoned spear that will slay the evil ogre of climate change.

And I did hear about a wide range of technologies that could one day suck billions of tons of carbon dioxide (CO2) from the atmosphere.

The ideas (described in detail below) included: growing millions of acres of switchgrass, grinding up alkaline rocks and chemically reacting them with CO2, building huge arrays of fans to scrub CO2 from the air, and dumping iron into the ocean to grow more plant-like plankton.

Unfortunately, the speakers mostly agreed that these so-called “climate interventions” make sense only if you’re also going to cut carbon emissions.

Sucking CO2 out of the atmosphere while simultaneously dumping more in at full tilt (by burning fossil fuels) would be like bailing out a leaking boat.

“If you’re looking for a quick little fix, it just isn’t there,” said Ken Caldeira, an atmospheric scientist at Carnegie Institution for Science. “The best thing to do is to build an energy system that doesn’t put CO2 into the atmosphere in first place.”

So much for that poisoned spear.

Still, the researchers agreed that it’s important to invest now in technologies to absorb CO2. If we can do that and cut emissions, there’s hope we can turn things around.

“The really big cost is delay,” said Jim Edmonds of the Joint Global Change Research Institute. “Delay greatly increases the cost of all these approaches,” he said.

The only idea I didn’t include is changing the atmosphere so it reflects sunlight back into space. The experts generally agree that’s a crazy idea.

Listed from greatest to least amount of carbon absorption possible by the year 2100:

1. Direct Air Capture and Sequestering (aka chemical scrubbing)

photo credit: Carbon Engineering

An array of fans draws air into a chamber where CO2 reacts with a liquid solution of an alkaline chemical, such as potassium hydroxide. Further reactions generate highly concentrated CO2 gas, which gets pumped underground and turned into stable, carbon-bearing rock.

Plants such as switchgrass are cultivated, and suck carbon out of the atmosphere as they grow. The harvested plants are processed to yield energy and CO2 gas. The CO2 is pumped underground where it reacts with minerals to form stable, carbon-bearing rock.

Would it work? Yes, at some scale; possible barriers to very large-scale deployment.

Drawbacks: Expanding to full potential would require up to a billion acres of cropland; large water and fertilizer requirements.

3. Ocean Iron Fertilization

photo credit: NASA

Dumping iron into the ocean boosts the growth of phytoplankton, tiny creatures that absorb CO2, as plants do. Unfortunately, this process could harm marine food webs in many ways.

Would it work? Probably, though more research is needed.

How much CO2 could it remove by 2100? 90–300 billion tons

Cost per ton removed: $400

Advantages: Some testing completed.

Drawbacks: Significant damage to marine ecosystems likely.

4. Forest Restoration and Low-Till Agriculture

Two low-tech ideas: First, replanting previously cut forests could provide natural carbon absorption via photosynthesis. Second, because tilling the soil releases CO2, the use of alternative tools such as seed drills for planting would keep more carbon in the ground.

Would they work? Yes; these are low-tech approaches.

How much CO2 could they remove by 2100? 100 billion tons

Cost per ton removed: $1–$100

Advantages: Technology ready to go; cheapest option available.

Drawbacks: Reforestation competes with farms that produce food.

5. Enhanced Weathering

Involves crushing rock containing silicon-bearing minerals—olivine, for example—which naturally react with CO2. Such minerals could either be combined with CO2 in a reactor on land, or spread over the ocean where they would react with CO2 in the water.

Workers maintain vehicles in a taxi garage in Queens, New York City, on Wednesday. The owner of the garage and taxis, who preferred not to be identified, said there are 1,000 plants in the shop (watered by hand twice weekly) and that they serve to clean the air: “I like to be in a nice environment, a clean environment. That’s why all my cars are hybrids and that’s why we have all the plants.”

Running parallel to the Pacific Ocean for nine miles, this BLM-administered coastal river is separated from the ocean by only a thin foredune of sand. Many rare birds, animals, and plants depend on New River’s estuary, forest, meadow, wetland, and shrub habitat for survival. Dedicated almost exclusively to Watchable Wildlife, the area remains secluded and primitive, providing nature enthusiasts with short, rustic, self-guided loop trails to view wildlife.

ACECs are places where special management attention is needed to protect and prevent irreparable damage to important historic, cultural and scenic values; fish, wildlife resources or other natural systems or processes; or to protect human life and safety from natural hazards. Learn more: http://bit.ly/blmacec.

Joshua Klein spent 10 years studying crows, mostly focusing on their intelligence and problem solving. After years of studying he made his own"Crow Vending Machine”, which is literally a vending machine for crows. One of the reason they are one of the most intelligent animals is because they are synanthropic, or hyper-adaptive and thrive from human industrialization (along with rats, roaches, etc.)

He tests their intelligence in a four-step system:

First the machine had some peanuts on the base and crows would come by, eat the peanuts and leave and then the machine spits up more nuts and then cycle continues and the crows keep coming back.

The second phase is simply adding coins that sit amongst the piles of nuts, and then within a few days the crows are acquainted with this too.

Once they’re used to the noise of the machine and its location they move on to the third phase.

The third phase had only a coin on the tray, but unlike most animals they don’t just inspect it and leave, they sweep it out of the way and eventually knock it down into the slot. That triggers the peanuts to come out of the machine. Soon enough, all of the crows know this and are doing it regularly. Once they are accustomed to that they move on to the final stage.

In the last stage the crows show up and nothing happens. They peck at the machine or look at it etc. Eventually the crows will notice some leftover coins on the ground and pick it up, drop it in the slot and so on and so forth.

This proves we could use crows for positive ways that will benefit both parties, ie. they throw away trash and get food in return